1. Field of the Invention
This disclosure is directed to an alternating copolymer of phenylene vinylene and oligoarylene vinylene, a preparation method thereof, and an organic thin film transistor comprising the same, and, more particularly, to an alternating copolymer of phenylene vinylene and oligoarylene vinylene, which comprises phenylene vinylene and oligoarylene vinylene alternating in the polymer backbone, and thus, when applied to the organic active layer of an organic thin film transistor, a high on/off current ratio and high charge mobility can be imparted while low off-state leakage current is maintained, and to a preparation method thereof and an organic thin film transistor comprising the same.
2. Description of the Related Art
Generally, an organic thin film transistor (OTFT) comprises a substrate, a gate electrode, an insulating layer, source/drain electrodes, and a channel layer, and is classified into a bottom contact (BC) type, in which a channel layer is formed on source/drain electrodes and a top contact (TC) type, in which metal electrodes are formed on a channel layer through mask deposition.
The channel layer of the TFT is typically formed of an inorganic semiconductor material, such as silicon (Si). Recently, however, in order to realize large, inexpensive, and flexible displays, the demand to use an organic semiconductor material, in place of an expensive inorganic material, requiring a high-temperature vacuum process, is increasing.
Thus, thorough research into organic semiconductor materials useful as the channel layer of OTFTs and transistor properties using the same is being conducted. Examples of low-molecular-weight or oligomeric organic semiconductor materials include merocyanine, phthalocyanine, perylene, pentacene, C60, or thiophene oligomer. Lucent Technologies and 3M reported the use of pentacene monocrystals to realize OTFTs having high charge mobility of 3.2˜5.0 cm2/Vs (Mat. Res. Soc. Symp. Proc. 2003, Vol. 771, L6.5.1˜L6.5.11).
In addition, OTFTs using a thiophene polymer as the polymer material have been reported. Although these OTFTs have properties inferior to those of OTFTs using low-molecular-weight material, they are advantageous with respect to the processability thereof because a large area may be realized at a low expense through a solution process, for example, a printing process. Further, the organic semiconductor polymer material has lower charge mobility than low-molecular-weight material, including pentacene, but is preferable thereto because it eliminates the need for a high operating frequency and enables the inexpensive fabrication of TFTs.
With the goal of commercializing the OTFTs, off-state leakage current, in addition to charge mobility, must be minimized. That is, a high on/off current ratio should be satisfied. To this end, various attempts to improve such properties are being made.